Hi jedwardsalt,
Thanks for your posting.
about your question, it doesn't effect the result of each self hosting widget in different version,
it means if you have exported by self hosting in v2.1, and then you upgrade to 2.5, the widget which exported by v2.1 will be nothing happened.
Compare to v2.1, it is little different exporting result in v2.5(2 folders and 1 html file), for example, i type flowing as my widget name, and i will get 2 folders and 1 html file as the following pic shown

and
1. Now you need to upload the _ShareFiles250 folder, the Flowing folder and the html file, to the Hosting URL using FTP.
2. for example
If you have typed in www.reallusion.com/widget in the Hosting URL, you must upload both folders inside the widget folder.
If you have typed in www.reallusion.com/widget/widgetcast you must upload both folders to the widgetcast folder which is under the widget folder.
that's all.
hope you enjoy it:D